1. Field of the Invention
The invention relates to a method for the production of a composite hollow body formed of aluminum alloys, the body being comprised of two layers of differing structure. The two layers are joined together perfectly, one of the layers being intended to operate in contact with a mobile surface, this layer being thereby useful as an internal combustion engine lining, a jack case, or any hollow body having a profile which is stationary or slightly variable over its length and which must have good resistance to friction.
2. Description of the Prior Art
In current technology, hollow bodies used in the manufacture of internal combustion engine linings are formed from a single material, such as cast iron or an aluminum alloy having a high silicon content. Prior methods for producing such a cast iron body include centrifugal casting. Such articles formed of aluminum alloy may either be molded or extruded by impact of cast discs as claimed in French Pat. No. 2,344,358, or, alternatively, by extrusion of particles as described in French Pat. No. 2,343,895. According to the extrusion method, the lining which is obtained has a particularly fine structure in which primary silicon crystals may have dimensions of less than 5 .mu.m. When the molding method is used, dimensions of less than 20 .mu.m cannot be obtained. The fine structure previously produced by the referenced extrusion process is particularly favorable in reducing the binding tendency of the linings, particularly when the linings operate in contact with pistons formed of aluminum alloy. In addition, the products formed by the particle extrusion method are easily machinable and allow the use of alloys which cannot be obtained by other production methods. Further, the addition of addition products, such as graphite, tin, or silicon carbide, to the linings formed by the particle extrusion method have greatly improved friction resistance. However, problems arise when hypereutectic silicon alloy mixtures and addition products are shaped as a tube by extrusion and then machined to produce a lining. In particular, it is difficult to avoid considerable adhesion to the tools and notably to the extrusion mandrel which necessitates working on a bridge die while applying considerable extrusion pressure. Moreover, the use of hypereutectic silicon alloys in the divided condition increases the cost price of the linings relative to the cost price which could be obtained using alloys shaped by means of casting. The present invention finds particular solution to the aforementioned problems by providing a method for producing a composite hollow body by particle extrusion techniques, the present method retaining the economical advantages of such techniques while eliminating certain vexing technical disadvantages associated therewith.